I'm working from a premise of not too formal, not too informal, not too ostentatious, not black and certainly not white. So that narrows it down 
My real question is: how close to white can you get without it being white? Is floral on a white base ok?
I've included a few here and would appreciate your thoughts on whether they are suitable. For further info: bride and groom are English, wedding is in 4 weeks and in a relatively unusual venue which might mandate wellies.....